After forming certain layers on a semiconductor substrate, an etch mask is utilized to pattern certain layers through a photo resist trimming process. While the photo resist trimming process is performed, the thickness of a photo resist pattern may be reduced. Moreover, the etch mask may also be etched away during the process, depending on an etching selectivity ratio of the layers and the etch mask. Therefore, the etch mask may not form the layers as a target pattern.
FIG. 1 is a plan view of a semiconductor device illustrating a method of manufacturing semiconductor devices using a conventional photo resist trimming process.
Referring to FIG. 1, a layer to be etched away is formed on a semiconductor substrate P1. The layer to be etched away may be a polysilicon layer for forming a gate of a transistor, or a nitride layer for forming a hard mask. After forming the layer to be etched away, a photo resist layer is formed on the layer to be etched away. Finally, the photo resist layer is exposed and developed by using a photo mask having a designed pattern so that photo resist patterns P2 are formed. The photo resist patterns P2 may be inferior. For example, there may be a bridge pattern D1 connecting the patterns P2, or there may be a deformity pattern D2 having a wider width.
A photo resist trimming process may be performed after the semiconductor substrate P1 is loaded on etching equipment, in order to achieve minimum marginal resolution critical dimension (CD) of the photo resist patterns P2. As a result, final photo resist patterns P2′ on which CD is much reduced, may be formed. The bridge inferior pattern D1 may be removed by the photo resist trimming process. The deformity pattern D2, however, may not be removed by the photo resist trimming process. Although the absolute width of the deformity inferior pattern D2 may be reduced, the relative width between the deformity pattern D2 and neighboring patterns may remain.
Moreover, the line width of the final photo resist patterns P2′ is reduced by the photo resist trimming process, but the thickness of the final photo resist patterns P2′ is thinner due to etching. Therefore, while the layer to be etched away is etched by using the final photo resist patterns P2′, the thickness of the final photo resist patterns P2′ is getting thinner as the etching process is going on. In conclusion, the final photo resist patterns P2′ may not perform an etching protection layer so that the pattern shape of the layer to be etched away may be abnormal, or a portion of the layer to be etched away may be removed in worst case.
As described above, in order to overcome marginal resolution of photo equipment, and reduce the pattern width of a layer to be etched away, a photo resist trimming process is performed. As a result, it may reduce the CD of photo resist patterns and remove bridge pattern D1. However, photo resist patterns may not perform the formation of etching protection layers normally so that it may cause deterioration of pattering characteristics and difficulty in removing deformity pattern D2. Moreover, it may be impossible to use the photo resist trimming process in order to both remove the bridge pattern and maintain the CD of pattern as it was.